ICD = International
Classification of
Diseases
http://www.youtube.com/watch?v=Q9Udj2QfO_U
NOTE: Obesity is included in the ICD-10 but not in the DSM-IV
as it has not been established that it is consistently associated
with a psychological or behavioural syndrome (APA, 2000)
DSM= Diagnostic and
Statistical Manual of
mental disorders
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1 in 2 adults in the US were either overweight
or obese in the 1990s (Tataranni, 2000)
In the UK there is an upward trend in obesity
◦ 1/2 women and 2/3 men are either overweight or
obese
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Obesity shortens life by an average of 9 years
(National Adult Office, 2001)
Mokdad et al (1999) refer to an “obesity
epidemic”
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The World Health Organization increases
risks of
◦ Type 2 diabetes
◦ High blood pressure
◦ Reduced life expectancy
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Masso-Gonzalez (2009) estimated the
incidence of diabetes in the UK between 1996
and 2005
◦ Type 1 was constant
◦ Type 2 increased from 46% to 56%
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Most common ways to define obesity are
◦ BMI (Body Mass Index)
◦ Waist circumference
◦ Measuring thickness of fatty tissue using callipers
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BMI is calculated dividing a person’s weight
by their height squared
BMI of less than 18.5=underweight
BMI over 25=overweight
BMI over 30=obese
BMI over 40=morbidly obese
ISSUES with BMI: doesn’t take into account the
ration between fat and muscle
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Emotional and restrained eating
Binge-eating disorder
Food addiction
Night eating syndrome
Psychological factors affecting physical
activity
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Behaviourist explanation: food is associated with stress
control
Emotional arousal =>dishinibition of
restraint=>emotional eating
Heatherton (1993) suggests that overeating constitutes an
escape from self-awareness in response to emotional pain
Emotionality theory of obesity (Schachter, 1968)
◦ People who become obese eat for emotional reasons
◦ Thin people eat for hunger
Overeating (hyperphagia) and under-eating (hypophagia)
were also considered a way of managing emotions by
Bruch (1965)
‘Restraint theory’ (Herman&Mack) shows how overeating
might actually be caused by restained eating
Psychodynamic: denial – “theory of ironic processes of
mental control” (Wagner,1994) – WHITE BEAR!
+Polivy&Herman (1999) told women they had
passed\failed a cognitive test – those who
had failed chose to eat as much as they liked
-there is contrasting evidence on the link
between stress and eating
+Verplanken et al. (2005) correlational analysis
on mood, impulse buying and snack
consumption
◦ Those with low self-esteem were more likely to
impulse buy and also consume snacks
◦ Possibly this behaviour is an attempt to cope with
the emotional distress caused by low self-esteem
-Today it is believed that many people eat in
response to their mood, regardless of their
size
+Herman&Mack “preload\taste-test” confirms
retraint theory
+ this helps explain why many people tend to
regain weight after dieting
-not all dieters regain weight (Ogden, 2000)
-issues with causality: overeating might be the
cause of low mood rather than the
consequence!!
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Approaches
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Issues
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Debates
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AO3
◦ alternative explanations (eg social; cognitive)
◦ Cognitive approach: motivation CAN reflect action
(social cognition models)
◦ Social approach: importance of cultural factors and
availability
◦ Ethical issues – causing guilt in obese individuals +
issues with preload\taste-test
◦ Gender bias
◦ Free will vs determinism
◦ Nature vs nurture
◦ Lack of ecological validity (artificial setting)
◦ PPs mostly females (lack of generalisability)
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Eating an objectively large amount of food
while experiencing a subjective sense of lack
of control
Usually develops during late adolescence or
early adulthood
It is usually associated with high levels of
depression, low self-esteem and body
dissatisfaction
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Wardle (1999) behind the food addiction model of
obesity is a model of addiction
◦ Exposure to a substance => changes to the CNS
◦ This explains withdrawal symptoms and craving
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Behaviourist approach: eating is maintained as a
consequence of negative reinforcement associated
with the avoidance\relief of withdrawal symptoms
Eating a small amount of the addictive food can
trigger a binge...
Carbohydrate craving hypothesis
Although obese people don’t seem to eat
necessarily more carbohydrates, but have a
preference for sweet, fatty foods
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Stunkard et al (1955)
◦ Evening hyperphagia: consumption of at least 1\4
of total daily calories after evening meal
◦ Insomnia (especially difficulties falling asleep)
◦ Morning anorexia (no breakfast)
◦ Recurring awakenings and failure to fall back asleep
without eating or drinking
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NES seems to be more common in obese
people than the general population
BUT there is little evidence of a relationship
between NES and obesity
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It is unclear whether reduced physical activity
is a cause or a consequence of obesity
Psychosocial factors implicated with lack of
exercise:
◦ Perceptions of competence
◦ Fear of displaying body in a public setting
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Other reasons might be lack of
opportunities\need
◦ eg using car and public transport + tv - p.181 book
Prentice&Jebb (1995)
◦ Move from agricultural to industrial society
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Rissanen et al. (1991) examined the
association between levels of physical activity
and excess weight gain of 12000 adults over
5 years
◦ Results: lower levels of activity were a greater risk
factor for weight gain than any other baseline
measure!
◦ BUT there could be a 3rd factor involved (eg those
with low activity were women with young children
so that could explain weight gain...)
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Cross-sectional design used to investigate
exercise\obesity (compare obese vs nonobese people)
Bullen et al (1964) used time-lapse
photography to observe obese vs normalweight girls on summer camp
◦ Obese girls spent more time floating than
swimming
◦ Obese girls were inactive for 77% of time when
playing tennis (vs 56% normal weight girls)
•Genetic
theories
•Neural model of obesity
•Evolutionary model of obesity
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Family clusters
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Twin studies
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Metabolic rate theory
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Appetite regulation
◦ If one parent is obese, 40% chance of child being obese
◦ If both parents are obese, 80%
◦ Probability of thin parents producing obese offspring is only 7%!
◦ MZ twins reared separately are more similar in weight than DZ
twins reared together!!!
◦ Stunkard et al (1990) examined the BMI of 93 pairs of MZ twins
reared apart and found that genetic factors accounted for 66-70%
of variance in body weight
◦ HOWEVER, role of genetics seems stronger in lighter twin pairs
than in heavier ones
◦ ‘resting metabolic rate’ s highly inheritable
◦ Tataranni et al (2003) – page 185 book- study on Pima Indians
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Appetite control may depend on a genetic
predisposition
A gene connected with profound obesity in
small animals has been identified BUT still
unclear for humans
Montague et al (1997) two children have been
identified with a defect in their ‘ob gene’,
which produces leptin
◦ They were given daily injections of leptin
◦ They lost 1-2 kg per month
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Possible neurochemical imbalances cause
overeating
Recent research suggests that body fat might
be an active organ and may trigger hunger
itself
This would mean that once individuals start
gaining excess weight, they then feel more
hunger and become less sensitive to satiation
signals
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Could storing excess body fat be an adaptive response?
‘Thrifty gene’ hypothesis (James Neel)
http://www.independent.co.uk/news/science/scientists-linkobesity-to-thrifty-gene-of-our-ancestors-596874.html
People from Africa, South-east Asia and Polynesia are especially
prone to obesity because they are more likely to have inherited
the genes that encourage the storage of fat, Jeffrey Friedman, an
obesity specialist at the Rockefeller University in New York,
writes in the journal Science.
Professor Friedman says that the difference in obesity rates
between ethnic groups could have something to do with their
respective genetic histories. "For people who lived in times of
privation, such as hunter-gatherers, food was only sporadically
available and the risk of famine was ever- present.
"In such an environment, genes that predispose to obesity
increase energy stores and provide a survival advantage in times
of famine. This is the so-called thrifty gene hypothesis," he says.
+explain why obesity often runs in family
+simple, effective explanations
+there is evidence for certain ethnic groups being
more predisposed to obesity
+reduce the risk of stigmatisation of obese individuals
-BUT might reduce effectiveness of dieting
-doesn’t explain why obesity is on the increase today,
whereas our gene pool has remained constant
-doesn’t explain why geographical relocation to
obesogenic environment often causes individuals to
gain weight
-it is still unclear how genes are involved in obesity and
to what extent...
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Free will vs. determinism
Nature vs. nurture
Low generalizability of case studies
Issues of extrapolation
Compare biological approach to behaviourist,
social learning, cognitive